1. Field of the Invention
The present invention relates to an operating device having an operating lever for operating a control valve connected to an actuator, especially an operating device mounted on a work vehicle.
2. Description of the Related Art
Such an operating device for a control valve, there has been known a device disclosed in Japanese patent application JP2004-360331A which includes: a first operating lever for operating a first control valve for controlling a boom cylinder, and a second control valve for controlling a bucket cylinder; and a second operating lever for operating a third control valve for controlling an actuator provided in a front loader. The first operating lever is supported by first and second supporting members, through a mount body whose upper face holds the first operating lever, and also through a swing frame to which the mount body is swingably connected by a second spindle. The swing frame is swingably supported by the first and second supporting members through a first spindle. The swing frame has a mount piece extending therefrom which is uniformly swingable with the swing frame. The mount piece is connected to a slidable spool of the first control valve through a first interlocking member which has a main link, an upper mount piece fixed to an upper portion of the main link, and a lower mount piece fixed to a lower portion of the main link. The upper mount piece is pivotally connected to the mount piece of the swing frame through a pin, and the lower mount piece is pivotally connected to the spool of the first control valve through a pin. The mount body has a spindle uniformly swingably attached thereto. The spindle is connected to a slidable spool of the second control valve through a second interlocking member which has a main plate, a mount shaft fixed to an upper portion of the main plate, and a lower mount piece fixed to a lower portion of the main plate. The mount shaft is connected to the spindle of the mount body through a ball joint, and the lower mount piece is pivotally connected to the spool of the second control valve. In the operating device having such a structure, the first operating lever is swingably operable about the axis of the first spindle and the axis of the second spindle. When the first operating lever is swingably operated about the axis of the first spindle, the swing frame is swung to push and pull the spool through the first interlocking member, which enables an operation of the first control valve. When the first operating lever is swingably operated about the axis of the second spindle, the mount body is swung to push and pull the spool through the second interlocking member, which enables an operation of the second control valve. The second operating lever is swingably and operably attached to a mount wall. The second operating lever has a boss portion and a connection arm which is uniformly swingably attached to the boss portion. The connection arm is connected to a slidable spool of the third control valve through a third interlocking member which has a main link, an upper mount piece attached to an upper portion of the main link, and a lower mount piece attached to a lower portion of the main link. The upper mount piece is pivotally connected to a connection arm of the second operating lever through a pin, and the lower mount piece is pivotally connected to the spool of the third control valve through a pin. Accordingly, when the second operating lever is swingably operated, the spool is slid through the third interlocking member, which enables an operation of the third control valve.
The operating device disclosed in Japanese patent application JP2004-360331A has a lock mechanism for locking the first control valve, the second control valve and the third control valve at a neutral state, with a use of a lock pin. In this lock mechanism, by shifting a locking lever connected to the lock pin through a support arm to thereby moving the lock pin along a bore in a pin holder, the lock pin is switched between a lock position and a lock release position. When the lock pin is switched to the lock position, a front end portion of the lock pin is inserted into insert holes of the first and second interlocking members, to thereby limit a movement of the first and second interlocking members, by which the first and second control valve are locked at a neutral state. A second lock portion formed in a rear end portion of the lock pin is fitted into a fitting portion of a through hole of a third interlocking member to thereby limit a movement of the third interlocking member, by which the third control valve is locked at a neutral state. When the lock pin is switched to the lock release position, the front end portion of the lock pin is removed from the insert holes of the first and second interlocking members, by which the locking of the first and second control valves at a neutral state is cancelled, and the second lock portion of the lock pin is removed from the fitting portion of the third interlocking member, by which the locking of the third control valve at the neutral state is cancelled.
In work vehicles, it is necessary to lock the control valves at a neutral state, in order to retain the work part in an operating state during a pause of working or during traveling. In the case where the above-mentioned conventional technique is applied, a feeling of locking operation tends to become heavy, or accuracy in locking tends to become poor. As a result, shakiness caused between the lock pin and insert hole of the interlocking member engaged with each other may adversely affect on the control valve. In order to make the feeling of locking operation lighter, the engagement of the lock pin with the insert hole should be facilitated. One possible solution is to make the insert hole larger. However in this case, shakiness caused between the lock pin and the insert hole engaged with each other becomes larger, and when the control valve is in a locking state, looseness (play) of the spool of the control valve becomes larger, due to shakiness caused between the lock pin and the insert hole.
On the other hand, in order to attain locking of the control valve with high accuracy, shakiness caused between the lock pin and the insert hole engaged with each other should be suppressed so as to suppress looseness of the spool of the control valve during a locking state. One possible solution is to make the insert hole smaller, just enough for the lock pin to be engaged. However in this case, the engagement of the lock pin and the insert hole with each other is less facilitated, and the feeling of locking operation becomes heavy.